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[ruby/bigdecimal] Fix the result precision of BigDecimal#divmod

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https://github.com/ruby/bigdecimal/commit/a32f6cb9e2
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Kenta Murata 2021-12-24 00:26:34 +09:00
parent 680a4ebb3c
commit a1d9fbef05
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GPG Key ID: CEFE8AFB6081B062
2 changed files with 21 additions and 6 deletions
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21
ext/bigdecimal/bigdecimal.c
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@ -1618,7 +1618,8 @@ BigDecimal_divide(VALUE self, VALUE r, Real **c, Real **res, Real **div)
/* For c = self.div(r): with round operation */ /* For c = self.div(r): with round operation */
{ {
ENTER(5); ENTER(5);
Real *a, *b; Real *a, *b, *d;
ssize_t a_prec, b_prec;
size_t mx; size_t mx;
TypedData_Get_Struct(self, Real, &BigDecimal_data_type, a); TypedData_Get_Struct(self, Real, &BigDecimal_data_type, a);
@ -1644,18 +1645,27 @@ BigDecimal_divide(VALUE self, VALUE r, Real **c, Real **res, Real **div)
TypedData_Get_Struct(rr, Real, &BigDecimal_data_type, b); TypedData_Get_Struct(rr, Real, &BigDecimal_data_type, b);
SAVE(b); SAVE(b);
*div = b; *div = b;
mx = (a->Prec > b->Prec) ? a->Prec : b->Prec; mx = (a->Prec > b->Prec) ? a->Prec : b->Prec;
mx *= BASE_FIG; mx *= BASE_FIG;
BigDecimal_count_precision_and_scale(self, &a_prec, NULL);
BigDecimal_count_precision_and_scale(rr, &b_prec, NULL);
mx = (a_prec > b_prec) ? a_prec : b_prec;
if (2*BIGDECIMAL_DOUBLE_FIGURES > mx) if (2*BIGDECIMAL_DOUBLE_FIGURES > mx)
mx = 2*BIGDECIMAL_DOUBLE_FIGURES; mx = 2*BIGDECIMAL_DOUBLE_FIGURES;
GUARD_OBJ((*c), VpCreateRbObject(mx + 2*BASE_FIG, "#0", true)); GUARD_OBJ((*c), VpCreateRbObject(mx + 2*BASE_FIG, "#0", true));
GUARD_OBJ((*res), VpCreateRbObject(mx*2 + 2*BASE_FIG, "#0", true)); GUARD_OBJ((*res), VpCreateRbObject(mx*2 + 2*BASE_FIG, "#0", true));
VpDivd(*c, *res, a, b); VpDivd(*c, *res, a, b);
return Qnil; return Qnil;
} }
static VALUE BigDecimal_DoDivmod(VALUE self, VALUE r, Real **div, Real **mod);
/* call-seq: /* call-seq:
* a / b -> bigdecimal * a / b -> bigdecimal
* *
@ -1736,6 +1746,7 @@ BigDecimal_DoDivmod(VALUE self, VALUE r, Real **div, Real **mod)
ENTER(8); ENTER(8);
Real *c=NULL, *d=NULL, *res=NULL; Real *c=NULL, *d=NULL, *res=NULL;
Real *a, *b; Real *a, *b;
ssize_t a_prec, b_prec;
size_t mx; size_t mx;
TypedData_Get_Struct(self, Real, &BigDecimal_data_type, a); TypedData_Get_Struct(self, Real, &BigDecimal_data_type, a);
@ -1793,8 +1804,10 @@ BigDecimal_DoDivmod(VALUE self, VALUE r, Real **div, Real **mod)
return Qtrue; return Qtrue;
} }
mx = (a->Prec > b->Prec) ? a->Prec : b->Prec; BigDecimal_count_precision_and_scale(self, &a_prec, NULL);
mx *= BASE_FIG; BigDecimal_count_precision_and_scale(rr, &b_prec, NULL);
mx = (a_prec > b_prec) ? a_prec : b_prec;
if (2*BIGDECIMAL_DOUBLE_FIGURES > mx) if (2*BIGDECIMAL_DOUBLE_FIGURES > mx)
mx = 2*BIGDECIMAL_DOUBLE_FIGURES; mx = 2*BIGDECIMAL_DOUBLE_FIGURES;

6
test/bigdecimal/test_bigdecimal.rb
View File

@ -1047,11 +1047,13 @@ class TestBigDecimal < Test::Unit::TestCase
a = BigDecimal('2e55') a = BigDecimal('2e55')
b = BigDecimal('1.23456789e10') b = BigDecimal('1.23456789e10')
q, r = a.divmod(b) q, r = a.divmod(b)
assert_equal((a/b), q) assert_equal((a/b).round(0, :down), q)
assert_equal((a - q*b), r)
b = BigDecimal('-1.23456789e10') b = BigDecimal('-1.23456789e10')
q, r = a.divmod(b) q, r = a.divmod(b)
assert_equal((a/b), q) assert_equal((a/b).round(0, :down) - 1, q)
assert_equal((a - q*b), r)
end end
def test_divmod_error def test_divmod_error